Sulfhydryl oxidase (SOX) is an enzyme known to be present in several mammalian biological systems including bovine milk, human skin, and bovine kidney. As of the date hereof, the biochemical role of the enzyme is unknown.
The SOX recovered from bovine milk catalyzes the following reaction: EQU 2R--SH+O.sub.2 .fwdarw.R--S--S--R+H.sub.2 O.sub.2
with a specificity toward the tripeptide glutathione (.delta.-L-glutamyl-L-cysteinyl-glycine). Many proteins in their reductively denatured state have been reported as substrates for the SOX-catalyzed reaction. Bovine ribonuclease is one such protein. A rather broad specificity of the SOX enzyme toward small molecular weight mercaptans as well as to proteins has been found to exist.
SOX is of interest in applications where oxidation of free sulfhydryls to disulfide linkages is sought, particularly in place of the non-specific oxidants such as hydrogen peroxide, peracids, borates, bromates, etc. which have been employed heretofore to effect the disulfide bond formation. The non-specific oxidizing capability of these agents is disadvantageous; unwanted side reactions may occur. Enzyme-catalyzed reactions provide the selectivity desired, thereby avoiding side reactions.
One instance known to the art wherein treatment with sulfhydryl oxidase is of value is for the removal of a burnt flavor from Ultra-High Temperature (UHT) sterilized milk. For details of such usage of SOX, reference is made to U.S. Pat. Nos. 4,087,328 and 4,053,644.
The inventors hereof believe that the mammalian source SOX described in U.S. Pat. Nos. 4,087,328 and 4,053,644 never will be available in large quantities at economic prices, but a microbial source could provide a readily available, commercially attractive supply of SOX.
The object of this invention is to provide a microbially derived SOX.